This invention is directed toward the field of colorimeters, and more specifically to colorimeters sealed in environmentally tight enclosures.
Colorimeters are well known devices used to characterize the color of an object and compare it to the color of other objects. The colorimeter provides illumination which is reflected or transmitted by the object and is transmitted optically to a dispersing element which disperses the coherent light spectrally. A detector array converts the spectra of the light into discrete signals which provide a color signature of the object. The signal is then sent to an A/D converter and then input into a microprocessor for processing. After the color signature has been generated by the detector array it may then be compared to signatures stored in memory.
There was a desire among some users of colorimeters to use the devices in industrial environments. Such use would expose a colorimeter to airborne dust and moisture, and occasionally to hose directed water. However, due to the nature of the colorimeter's components, such an environment would cause colorimeters to fail.
Yet, merely enclosing a colorimeter in an environmentally tight enclosure is not a complete solution to the problem. Both the National Electrical Manufacturers Association (NEMA) and Underwriter's Laboratory (UL) have issued standards which require that the external surface temperature of such a device be no greater than 70 degrees C., with an external ambient of 40 degrees C. Both the lighting means and the processing electronics radiate heat, at least some of which must be dispersed to meet the NEMA and UL standards.
Further, halogen lamps, which were often used as the source of illumination, have a regenerative cycle which is dependent upon the temperature of the surrounding air. Such a halogen lamp must be kept at a constant preselected temperature in order to maximize lamp life.
Thus, it is an object of the present invention to provide a colorimeter which is environmentally sealed from the surrounding environment while still allowing for cooling of the processing electronics and lighting means.